-LRB- CNN -RRB- -- It was supposed to be a couple 's little getaway , on a little plane , from upstate New York to the Florida coast .

It turned into a tragedy .

The saga of the single-engine TBM-700 aircraft also turned into an international incident , spurring both the United States and Cuba to dispatch fighter jets to trail the plane after it went radio silent .

So what happened ? Why might a plane 's crew go unresponsive for over four hours , drifting southward over the U.S. mainland , the Atlantic and eventually into the Caribbean as it did ? The North American Aerospace Defense Command , or NORAD , tweeted it might have been a case of hypoxia , a condition that sets in when a person does n't get enough oxygen -- as can happen if there 's an airflow problem high in the sky .

What is hypoxia ?

The best clues , so far , lie in what U.S. fighter jet pilots saw as they looked into the aircraft : the pilot slumped over and the windows frosted over .

Then there was the radio communication , which the Federal Aviation Administration says ended around 10 a.m. ET . At that time , the plane was somewhere above Statesville , North Carolina , about 600 miles south of the Rochester , New York , airport it left from around 8:45 a.m. destined for Naples , Florida .

The pilot asks to descend to 18,000 feet because `` we have an indication that is not correct in the plane , '' according to a stream of that transmission posted on LiveATC.net .

The air traffic controller told the pilot to `` stand by , '' then to proceed to 25,000 feet as he works on clearing the plane to go lower . The conversation continues off-and-on for over four minutes , though it 's largely one-sided : The pilot is n't clear in his remarks , nor does he ever declare any sort of emergency .

At one point , he simply repeats his call sign twice when the controller asks if he heard the request to drop down to 20,000 feet .

Data indicates the plane did n't drop . It cruised for hours some 25,000-feet above the ground .

Until sometime before 2:15 p.m. , that is , by which point estimates suggested the fuel would have run out .

The aircraft , by then , had slowed considerably -- down to 176 knots -LRB- 200 mph -RRB- , from a consistent 308 knots for most of its flight .

And it stopped altogether after crashing 14 miles off Jamaica 's northeast coast .

Larry , Jane Glazers ' children ` devastated '

The watery crash spurred Jamaica and the United States to swiftly dispatch government aircraft to the scene . By early evening , Jamaican authorities had found an oil slick in the prime search area that -- at that point -- was the only possible sign of the downed aircraft , according to Maj. Basil Jarrett of the Jamaica Defense Force . This differs from earlier reports that a `` wreckage field '' had been spotted .

'' -LRB- The search -RRB- is fairly unpredictable given the size of the area and given the conditions out there , '' said Jarrett , who said the operation would stop at nightfall before resuming Saturday morning with assistance from a U.S. Coast Guard cutter . `` It 's very difficult to say what we will be able to recover and when . ''

As they searched , the Glazer family of Rochester , New York , mourned .

The U.S. Coast Guard issued a statement indicating there were `` three people reportedly aboard '' the plane . Yet Scott Fybush , the family spokesman and also the Glazers ' nephew , said he believed the couple were the only people on the plane , with Larry Glazer flying the couple toward their vacation home in Florida .

While there was no official announcement immediately on the fate of those on the plane , the Glazers ' children said in a statement they were `` devastated by the tragic and sudden loss of our parents . ''

Politicians in New York hailed the couple for their business and charitable endeavors , with Gov. Andrew Cuomo calling them `` innovative and generous people who were committed to revitalizing downtown Rochester and making the city they loved a better place for all . ''

Larry Glazer co-founded Buckingham Properties in 1970 , a year after graduating from Columbia University . According to his official bio , the company owns and manages more than 50 properties totaling over 9 million square feet in the Greater Rochester area .

Jane Glazer founded QCI Direct , a 100-employee company that has an outlet store and makes `` two national retail catalogs mailed to 35 million people annually , '' according to its website .

A post on Women Entrepreneurs Blog , which is produced in conjunction with the University of Rochester 's business school , notes that she ran the New York City Marathon , did whitewater rafting and learned how to fly a plane -- all in addition to raising three children and building her business .

The Glazers ' children acknowledged late Friday afternoon that they `` too are waiting for answers . '' As they do , they took the chance to remember their parents and to express appreciation to those who were quick to offer condolences .

`` They loved and appreciated the opportunity to help build the community of Rochester , and we thank everyone in the community for their expressions of support , '' the children said .

U.S. , Cuban fighter jets trail aircraft

While authorities do n't know everything that went on inside the plane , including what caused it to crash , they have spoken about what they did in response .

The government response started with those air traffic control communications -- and the alarming lack thereof .

The unresponsiveness spurred NORAD to dispatch two F-16 fighter jets set from McEntire Joint National Guard Base in Richland County , South Carolina , to investigate . NORAD said another pair of fighter jets out of Homestead , Florida -- F-15s -- took over around 11:30 a.m. and escorted the plane as it continued south past the U.S. mainland .

The American fighter jets broke off their pursuit 12 miles off Cuba , at which point the TBM-700 plane was still cruising at about 25,000 feet .

A Cuban fighter jet took over trailing the aircraft as it flew near that Caribbean island , according to NORAD .

Their longstanding public enmity notwithstanding , Cuba was cooperating fully with the United States on the matter and did not consider the plane 's movement a violation of its airspace , according to a Cuban source involved in conversations between the two nations . The Cuban government even let the U.S. Coast Guard 's C-130 aircraft go through its airspace and also gave permission for American `` military aircraft , if necessary , '' according to an official statement .

But none of these efforts , from either of these countries , could do anything about the doomed TBM-700 aircraft before it dropped off radar -- according to the flight tracking site , FlightAware.com -- at 2:11 p.m.

Both Glazers knew how to fly , although Fybush said Jane Glazer 's ability to fly legally may have lapsed .

The plane itself was owned by Larry Glazer 's company , Buckingham Properties . It was built by the French manufacturer Daher-Socata and powered by one Pratt and Whitney engine .

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2012 : Small plane with unresponsive pilot crashes into Gulf of Mexico

CNN 's Chelsea J. Carter , Aaron Cooper , John Newsome , Margot Haddad , Mike M. Ahlers , Patrick Oppmann , Ray Sanchez , Rande Iaboni and Deanna Hackney contributed to this report .

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NEW : Cuba : U.S. -- including `` military aircraft , if necessary '' -- had OK to use its airspace

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Pilot told air traffic control something was `` not correct , '' but did n't declare an emergency

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U.S. and Cuban aircraft tried to track the small aircraft , but neither could alter its course

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The plane crashed about 14 miles off the coast of Jamaica , authorities say